二段式吸收塔强化水洗技术提纯沼气过程

压力水洗技术已成为提纯沼气的关键技术之一。采用填料吸收塔进行CO_2脱除实验研究,考察了液气比、吸收压力、吸收温度、CO_2初始含量、填料层高度对CO_2脱除率的影响,以及液气比、沼气流量对总体积吸收系数的影响,并运用填料塔与喷雾塔结合的二段式吸收塔进行压力水洗提纯沼气的过程强化实验。实验结果表明,吸收压力和液气比的增大、吸收温度的降低、填料层高度的增加有利于CO_2的脱除,体积总吸收系数随着液气比及沼气流量的增加而增大。二段式吸收塔能够提高CO_2吸收效果,当沼气处理量为10 L·min-1,填料层高度为100 cm,CO_2含量小于3%时,与填料塔相比二段式吸收塔可以减少约12%的吸收液用量,并且采用110 cm填料的二段式吸收塔获得最佳的提纯效果,CO_2脱除率达到97.4%。     

富氧燃烧烟气压缩净化及高浓度CO2制备工艺研究

富氧燃烧技术是目前最有可能大规模推广和商业应用的碳捕集与封存技术之一,其中,烟气压缩净化及CO₂提纯对于整个富氧燃烧系统至关重要。然而,目前研究多聚焦于富氧燃烧后烟气压缩净化的工艺验证,而对烟气压缩纯化各单元运行特性的研究仍不深入,特别是烟气压缩净化过程杂质污染组分的迁移转化、系统运行参数与污染物脱除效率的关联仍不明确。且现有研究对净化后烟气的深度提纯及高浓度CO₂制备的关注也相对较少,直接关系到富氧燃烧系统运行经济性。因此,针对富氧燃烧烟气净化及CO₂提纯需求,系统探究了富氧燃烧烟气压缩纯化过程SO₂、NO_x吸收脱除以及CO₂深度提纯等各子系统的运行特性,其中SO₂与NO_x脱除采用压缩-酸液吸收,CO₂深度提纯采用低温精馏。结果表明:通过烟气净化可实现SO₂脱除效率达100%,NO脱除效率达99%,同时实现纯度为99.99%的食品级液态CO₂制备。烟气净化过程中,气相反应占据主导,提高压力可缩短反应时间;当SO₂吸收塔运行压力超过0.8 MPa时,SO₂脱除效率可达100%;当NO吸收塔运行压力超过3.0 MPa时,NO排放浓度可达超低排放标准。CO₂提纯过程中,提高压力会降低液体CO₂纯度。SO₂吸收塔运行压力为1.6 MPa、NO吸收塔运行压力为3.0 MPa、CO₂提纯塔运行压力为3.8 MPa时,系统整体功耗最低,为0.37 MJ/kg。     

沼气提纯过程中醇胺溶液吸收CO2传质性能

醇胺溶液吸收CO₂是沼气提纯领域重要的研究课题。在实验填料吸收塔中,以乙醇胺(MEA)、二乙醇胺(DEA)为吸收剂,研究了吸收剂浓度、进气流量、CO₂浓度、进液温度对吸收过程转化率η、吸收速率N以及气相总体积传质系数K_Ga_e的影响。结果表明,吸收剂浓度增加可有效提高η、N及K_Ga_e;进气流率增加,η逐渐降低,N先增加后降低,K_Ga_e先增加后降低最终趋于稳定;随着CO₂浓度增加,η和K_Ga_e不断降低,N逐渐增加;随着进液温度升高,η和K_Ga_e均先升高后降低;MEA、DEA的最佳进液温度在40～60℃之间,并随CO₂负载量增大而逐渐降低。研究结果对于醇胺溶液吸收法沼气提纯技术的研究开发和实际应用有参考作用。     

填料吸收塔内乙醇胺溶液吸收CO2增强因子

醇胺溶液吸收CO₂是沼气提纯领域重要的研究课题。在实验填料吸收塔中,以NaOH水溶液吸收低浓度CO₂的实验结果估算了填料的有效相界面积,建立了乙醇胺（MEA）溶液吸收高浓度CO₂增强因子的数学模型,并从数学模型和实验的角度研究了MEA浓度、进气流率、CO₂浓度等工艺参数对MEA吸收CO₂增强因子的影响。结果表明,增强因子数学模型计算值与实验值能够良好吻合,MEA吸收CO₂化学反应增强因子随进气CO₂浓度增加而降低,随MEA浓度增加而增加,随进气流率增加而减小。     

真空变压吸附提纯沼气的实验

以煤基碳分子筛为沼气净化吸附剂,借助扫描电镜观察了碳分子筛的表面形貌,并通过物理化学吸附仪表征了碳分子筛的孔径分布。基于静态容积法测定了CO₂与CH₄在碳分子筛的静态吸附量,并估算了CO₂与CH₄在碳分子筛的动力学扩散系数。单塔穿透实验考察了吸附压力与进料流量对原料气中CO₂穿透曲线的影响,选取吸附压力为0.3 MPa,进料流量为4 L·min-1进行两塔六步真空变压吸附提纯沼气的实验研究,并考察了吸附步骤时长与产品气冲洗率对CH₄富集效果的影响。实验结果表明,吸附步骤时长为140 s,冲洗率为0.05时,产品气中CH₄纯度可达98%,收率可达82%。     

乙醇胺捕集燃煤烟气二氧化碳工艺模拟

有机胺法是最有效的燃煤烟气二氧化碳（CO₂）捕集技术之一。使用Aspen plus模拟乙醇胺（MEA）捕获烟气CO₂的过程,先进行单独的吸收塔与再生塔模拟,在单独系统模型收敛的基础上,再进行吸收-解吸的综合模拟。在入塔烟气流量为8.22 m³/min、CO₂物质的量分数为0.18、MEA流量为2 311.3 kg/h、MEA物质的量分数为0.12条件下,MEA捕集燃煤烟气中CO₂的模拟结果: CO₂脱除率为69.3%,净化气中CO₂物质的量分数为5.33×10^-2,再生塔顶再生气中CO₂物质的量分数为0.956,基本达到了设计要求。此为更深入地开展胺法吸收CO₂的研究提供了依据。     

MDEA-PZ脱碳工艺模拟与优化

使用Aspen Plus流程模拟软件,为一套采用甲基二乙醇胺(MDEA)和哌嗪(PZ)作为复合吸收溶剂的166 752 m³/h(干基)原料气脱碳流程建立了模型系统。模拟结果表明,应在保证吸收和再生效果以及塔不发生液泛的前提下,优选MDEA-PZ溶剂法脱碳工艺流程中塔设备的理论板数、填料高度以及塔直径。吸收塔填料高度具有较大设计裕量,有效板数大于16块时即可满足传质要求;随着再生塔下段塔板数的增加,CO₂的再生量随之升高,表明接触气提时间越长,越有利于CO₂的再生,再生塔下段塔板数为25块时可以满足要求;再生塔上段塔板数大于15块即可满足要求。     

疏水性单管陶瓷膜接触器在SO2吸收中的应用

对平均孔径200 nm的氧化锆陶瓷膜进行疏水改性与表征,并将其组装制成疏水性单管陶瓷膜接触器,采用清水作为低成本吸收液,开展了陶瓷膜接触器在废气脱硫方面应用的研究。比较了亲、疏水陶瓷膜接触器的传质性能,考察了进气流量、吸收液流量、进气浓度和吸收液温度等因素对SO₂脱除率和传质速率的影响,并对陶瓷膜接触器进行了长期稳定性测试。研究表明,疏水改性只改变陶瓷膜的表面性质（接触角达到132°）,对形貌结构影响较小;与未改性的陶瓷膜相比具有更高的脱硫效率和总传质系数。SO₂的脱除率和传质速率随吸收液流量的增加均增加;SO₂的脱除率随进气流量和进气浓度的增加而降低,但传质速率增加;吸收液温度的升高不利于SO₂的吸收;原料气中的CO₂对SO₂的脱除率影响较小。与传统的填料塔相比,陶瓷膜接触器具有更小的传质单元高度（HTU）值。陶瓷膜接触器脱硫效率高,可稳定操作,在废气脱硫方面具有良好的应用前景。     

规整填料塔中氨水吸收CO2的体积总传质系数

目前,CO₂排放问题已经成为世界各国可持续发展面临的重要挑战。以化学溶剂吸收法工艺为基础的燃烧后脱碳是当前比较成熟的已进入工业规模实验的技术路线。而氨水作为一种新的吸收剂受到广泛关注。以气相体积传质系数（K_Ga_e）作为表征,对规整填料塔中氨水吸收CO₂的传质性能进行了研究,探索了气速、CO₂分压、液速和氨水浓度对K_Ga_e的影响。实验结果表明,在本文的工况条件下,K_Ga_e随液速和氨水浓度的增大而增大,随CO₂分压的增大有所减小,气速对K_Ga_e的影响不大。实验结果对今后填料塔的设计工作的经济性和合理性有一定指导作用。     

磁场对氨水吸收烟气中CO2的促进作用

开发了一种新型磁场辅助氨法烟气脱碳技术。含碳烟气通入混有磁性颗粒的氨水溶液,在外加磁场的作用下发生脱碳反应。对该技术的运行特性开展了实验研究。结果表明,外加8 mT恒稳磁场,2 g·L^-1纳米级Fe₃O₄颗粒,氨水的CO₂脱除效率比不添加磁场和颗粒时最多可提高8.8%。外加磁场可以有效提高低浓度氨水的CO₂脱除效率。在模拟烟气流量增加时,外加磁场能有效减缓CO₂脱除效率下降的趋势。同时,外加磁场使得CO₂脱除效率曲线向低温方向移动5℃,有助于提高低温条件下的CO₂脱除效率。磁场可提高气液接触效率、降低相间传质阻力、增强氨水反应活性,从而提高氨水吸收CO₂性能。     

聚氨酯合成革湿法生产废气中DMF的回收工艺

A new recovery technology is developed to recycle N,N-dimethyl formamide （DMF） in waste gas from wet type polyurethane synthetic leather industry. Given that the concentration of DMF in waste gas was as low as 325.6- 688.3 mg·m^-3, it was necessary to make sure two phases contact adequately and strengthen the mass transfer by increasing contact area and enhancing the turbulence. Therefore, two-stage countercurrent absorption and two-stage fog removing system were introduced into the technology. The top section of the absorption column was filled with structured wire-ripple stainless steel packing BX500, while the lower section with sting-ripple packing CB250Y. Total height of packing material was 6 m. In addition, there were both two-stage fog removing layer and high efficiency liquid distributor at the column top. All the operating parameters, including temperature, pressure, flow rate and liquid position, could be controlled by computers without manual operation, making sure the outlet gas achieved the national emission standard that the DMF concentration should be below 40 mg·m^-3. The whole equipment could recover 237.6 t of DMF each year, with the profit up to CNY 521×10^3.     

Simultaneous Absorption of Hydrogen Sulfide and Carbon Dioxide into di-isopropanolamine Solution

The simultaneous absorption of hydrogen sulfide and carbon dioxide into di-isopropanolamine (DIPA) solution was investigated in a 183 cm long, 2.72 cm OD wetted-wall column at atmospheric pressure. The influence of liquid flow rate, gas flow rate, temperature and liquid concentration on the absorption rate, overall gas-phase mass transfer coefficient and selectivity factor were studied at a constant gas feed ratio. The results show that the absorption rate of CO₂ increases rapidly with increasing liquid flow rate (the Reynolds number of the turbulent liquid film ranges from 2600 to 4350) but increases moderately with increasing gas flow rate (G = 18-91 L/min), indicating that it is liquid-phase mass transfer controlled. In contrast, the absorption rate of H₂S increases very slowly with increasing liquid flow rate but increases rapidly with increasing gas flow rate, indicating that it is gas-phase mass transfer controlled. The absorption rate of CO₂ also increases with increasing temperature (26-80°C) but H₂S absorption rate decreases with increasing temperature. When the concentration of DIPA solution increases from 0.2 to 2.6 mol/L, the absorption rate of both CO₂ and H₂S increases but with a larger rate of increase for CO₂ For selective H₂S removal, it is preferable to operate at low liquid and high gas flow rates, low temperatures and low DIPA concentrations.     

填料塔中氨水吸收二氧化碳的传质性能

在填料塔中对氨水吸收二氧化碳的传质性能进行了实验研究,测定了填料塔单位体积的有效传质面积aV,气相传质系数kG和体积总传质系数KGaV等,实验结果表明,随着气体流量增加,aV值略有上升,kGaV和kG值明显增大;体积总传质系数KGaV值也随着气体流量和氨水浓度的升高而增大。在总传质阻力中,气膜阻力所占比例相对较小,氨水吸收二氧化碳的过程主要受液膜阻力的控制。     

A review of chemical absorption of carbon dioxide for biogas upgrading

Significant attention has been given to biogas production, purification and upgrading as a renewable and clean fuel supplement. Biogas is a product of an anaerobic digestion process comprising methane, carbon dioxide, and trace amounts of other gases. Biogas purification removes trace gases in biogas for safe utilisation. Biogas upgrading produces methane-rich biogas by removing bulk carbon dioxide from the gas mixture. Several carbon dioxide removal techniques can be applied for biogas upgrading. However, chemical absorption of carbon dioxide for biogas upgrading is of special significance due to its operation at ambient or near ambient temperature and pressure, thus reducing energy consumption. This paper reviews the chemical absorption of carbon dioxide using amine scrubbing, caustic solvent scrubbing, and amino acid salt solution scrubbing. Each of these tech-niques for biogas upgrading is discussed. The paper concludes that an optimised implementation of the chemical absorption techniques for biogas upgrading requires further research.     

Interfacial area and mass transfer in gas-liquid cocurrent upflow and countercurrent flow in reciprocating plate column

The volumetric mass transfer coefficient and the interfacial area were measured for carbon dioxide absorption into water using a reciprocating plate column of plate geometry different from a Karr column. The specific interfacial area was governed by a change in bubble size at low agitation rates and by a variation in gas holdup at high agitation rates. The liquid phase mass transfer coefficient was strongly influenced by the agitation rate, the phase velocities and the plate geometry.     

Gas absorption with wetted-wick column

The newly designed wetted-wick column was constructed by using fiber glass and wire mesh and studied to investigate its feasibility as an alternative to the conventional packed tower in gas purification processes. Absorption of carbon dioxide in water for physical absorption and in aqueous mono-ethanolamine (MEA) solution for chemical absorption were employed for this investigation. A comparison with the packed tower, based on overall mass transfer coefficients (K_OGa) and height of transfer units (HTU_OG) at the same range of operating conditions, feed gas compositions, and gas retention time was made. High mass transfer coefficients (K_OGa) and low heights of transfer unit (HTU_OG) were obtained for the wetted-wick column. The high efficiency of mass transfer was caused by a number of factors: the separate passage of liquid and gas flow, an increased wetting surface, a longer period of residence time of the liquid and gas stream, and an increased interfacial area. The present study shows that the wetted-wick column is a highly recommendable device as an alternative to the packed tower in gas purification processes, either for physical gas absorption or for chemical gas absorption.     

上流式反应器气液相间传质特性的实验研究

上流式反应器设置在固定床渣油加氢反应器前有利于提高渣油原料适用性,延长装置运行时间。实验研究了上流式反应器气液相间传质,采用五齿柱形氧化铝催化剂模拟工业催化剂颗粒,水溶液模拟渣油,空气模拟氢气,采用无氧水物理吸收和亚硫酸钠化学吸收的方法,测定了在高气液比的条件下上流式反应器床层气液相间传质特性实验。考察了表观气速、表观液速、填料粒径、内构件、催化剂级配和床层高径比对液相体积传质系数和气液相界比表面积的影响规律。实验数据表明,液相体积传质系数随着气、液速的增大而增大;随填料颗粒增大而减小;在床层内安装合适的内构件或增大反应器高径比,能够促进气液相间传质。基于实验数据拟合了适合上流式反应器液相体积传质系数和气液相界比表面积的经验关联式,拟合误差最大分别为12%和24%;表明所建气液相间传质的经验关联式能更好地预测上流式反应器中的气液相间传质特性。     

多级雾化旋转填料床的传质性能

以两级雾化超重力旋转床为例,用化学吸收法考察了超重力因子β、液体流量、气体流量等对体积传质系数kyα的影响。结果表明:多级雾化超重力旋转床的体积传质系数随气液流量的增加而增加,在β较小时,实验曲线的斜率较大,kyα随β的增加急剧增加;但是当β超过100后,曲线的斜率减小,kyα随β的增加缓慢增大。     

填料塔中哌嗪二胺吸收低浓度SO_2的传质性能

为满足有机胺法脱硫设计开发的需要,采用动态吸收法测定了填料塔中哌嗪二胺(PA-A)水溶液吸收低浓度SO2的体积总传质系数KGa,考察了吸收工艺参数如吸收液中的PA-A浓度和初始pH值、液相流率、吸收温度、进气SO2浓度及流速等对KGa的影响。结果表明:KGa随着吸收液中的PA-A浓度和初始pH值、液相喷淋密度的增加而增大;随着吸收温度、气相流率及进气SO2浓度的增加而减小。通过实验结果分析得到体积总传质系数KGa与气液相流率比(qG/qL)之间符合指数关系式,该经验关系可用于工程设计计算。     

CO2 Absorption Behavior with a Novel Random Packing: Super Mini Ring

Abstract

For the purpose of capturing CO₂ from flue gas the absorption of CO₂ into an aqueous solution of monoethanolamine was measured by using a column packed with a novel packing, Super Mini Ring (SMR). The SMR gave a higher absorption performance relative to pall ring packing due to a larger effective surface area and also reduced the frictional pressure gradient. The absorption mechanism was observed to be mainly gas phase controlling. It was concluded that for the treatment of flue gas the SMR packing could reduce the height of the absorption column by 20% relative to a pall ring packed column.